Iohexol is a known contrast agent having the following structure:

Oral solutions of iohexol are useful as contrast agents for e.g. abdominal imaging by tomography. It is convenient to provide iohexol for such purposes in a solid form which can be reconstituted into an oral contrast solution prior to use. However, although iohexol is highly soluble in water, iohexol particles tend to form large, cohesive, sticky aggregates which dissolve very slowly. Typically, complete dissolution requires extended stirring or elevated temperatures which can lead to degradation of the iohexol in non-buffered systems. Since it is desirable to reconstitute solid (e.g. powdered) iohexol by manually mixing the solid iohexol composition in an appropriate diluent (e.g. water or a flavored aqueous solution) at the physician's office or at an imaging facility, there is a risk that the iohexol composition will not completely dissolve under such conditions, and therefore the patient will receive a lower concentration and dose of the iohexol contrast agent than is desirable for proper imaging. Accordingly, it is important that the iohexol be provided in a form that dissolves rapidly and completely when subjected to manual mixing conditions so that the patient is provided with the full dosage of iohexol, at the proper concentration.